Washington - The U.S. launched airstrikes in Yemen on Thursday that killed as many as seven militants, the second American missile attack in the country since the CIA and other spy agencies disrupted an al-Qaida airline bomb plot, U.S. officials said.

The strike came as new details surfaced about the foiling of the plot, including the disclosure that the operative who posed as a willing suicide bomber and later turned the device over to authorities was recruited in Britain by that country's spy service.

The operative's background as a Saudi living in Britain helps to explain why he may have been selected by al-Qaida's affiliate in Yemen to smuggle an advanced explosive onto a U.S.-bound flight. In reality, officials said, the operative was working as part of an elaborate espionage mission directed by the CIA and its Saudi counterpart.

The CIA declined to comment on any aspect of the mission or the airstrike. But officials from the United States and allied governments who spoke on the condition of anonymity confirmed the details about the operative's background.

Officials said the purported would-be bomber had been in place for months and had gained the confidence of senior al-Qaida figures, who sought to take advantage of his Western passport and other travel documents.

A Western intelligence official described the operation as a "joint venture" that relied on cooperation among multiple agencies to put the operative in position to penetrate al-Qaida in the Arabian Peninsula, or AQAP.

After taking possession of the bomb, the operative turned it over to Saudi handlers in Yemen before leaving the country. The device is in FBI custody in the United States and is being examined to determine whether it would have been detected by airport security systems.

The operative was among a network of informants in Yemen working on behalf of the CIA as well as the Saudi and Yemeni spy services. The informants have provided intelligence used in targeting for an escalating campaign of U.S. drone strikes.

The latest strikes, aimed at al-Qaida operatives in southern Yemen, bring the total this year to at least 15, about as many as in the previous 10 years combined. U.S. officials said it was too early to determine whether any high-value targets had been killed in the Thursday attack and declined to say whether it had been carried out by the CIA or the U.S. Joint Special Operations Command, which also patrols Yemen with armed drones and conventional aircraft.

A strike Sunday killed a senior operations leader in AQAP, Fahd al-Quso, who is thought to have been involved in the airline plot and was wanted for his role in the 2000 bombing of a U.S. warship on Yemen's shore, U.S. officials said.

The bombmaker suspected of designing the latest device, Ibrahim Hassan al-Asiri, has eluded U.S. and Yemeni authorities.

Defense Secretary Leon Panetta said Thursday that disclosures about the bomb plot have hurt intelligence efforts and that he supports the decision by Director of National Intelligence James Clapper to open an investigation into the leaks.

To counter the al-Qaida threat, "you have to protect" the agents who are used to penetrate such organizations, Panetta said, "and you have to protect the confidence" that foreign intelligence services have in their collaborations with the CIA.

Panetta also defended the administration's assertions that it has weakened AQAP, despite the group's expansion in southern Yemen over the past year and its ability to continue to plot attacks against the United States.

"We have been very successful at going after the leadership," Panetta said. "But, you know, they are a threat."